Synthesis of energy-induced waste minimization networks (EIWAMINs) for simultaneous waste reduction and heat integration

Abstract

This article introduces a process synthesis methodology for identifying cost-effective Energy-Induced Waste Minimization Networks (EIWAMINs). The synthesis methodology is targeted toward retrofit designs for an existing plant or site where environmental emissions (aqueous or gaseous) must be reduced. This approach uses heat-induced separation units that separate mass via a phase change (condensers, dryers, crystallizers, evaporators, etc.) and heat exchangers to simultaneously address waste minimization and heat integration within a large plant or site. While heat-induced separators may be employed for optimal waste separation and allocation (via a phase change), heat exchange equipment (e.g. heaters, coolers, chillers, etc.) may be employed to improve the thermodynamics of existing unit operations. In addition, pressurization/depressurization devices (compressors, turbines, etc.) are also employed to enhance the effectiveness of the heat-induced separators. The problem is tackled via two mathematical formulations which are mixed-integer non-linear programs (MINLPs). The mathematical formulations are combined to identify the most cost-effective design(s) that simultaneously addresses the plant waste minimization and heat integration tasks. Linearization techniques and graphical insights are incorporated to simplify the mathematical formulation of the problem. A case study is provided to highlight the features of this design procedure and its economic merits against several alternative designs.